This invention relates to a lubricating oil heater apparatus of an electric motorcar for adjusting temperature of the lubricating oil supplied to power transmission means of the electric motorcar in order to attain a smooth driving.
Viscosity of lubricating oil in a lubricating system of a motorcar varies so as that it is high at lower temperature and becomes lower as the temperature rises.
When there is a heat source apt to be high temperature like an internal combustion engine, the lubricating oil is used also for cooling surroundings of the piston for example, and its temperature rises without a special apparatus so that the lubricating oil can get to a moderate viscosity and achieve a sufficient lubricating function.
However, in a very cold area, sometimes starting of the engine is difficult because viscosity of the lubricating oil has been increased on starting.
Therefore, there is an example that a sheath heater is provided on an internal combustion engine or a transmission (Japanese Patent Publication No. Hei 6-29536). In this example, the lubricating oil is previously heated to reduce the viscosity by connecting a lead line extended from the sheath heater to a commercial alternating current source before starting the engine, so that the engine can be started smoothly.
But in case of the electric motorcar, heat generation of the motor which is the drive source is less compared with the internal combustion engine and there is no other heat source so that when the atmospheric temperature is low, even in running, temperature of the lubricating oil is lowered to increase the viscosity by air cooling effect owing to the running. Therefore, the lubricating oil in a power transmission mechanism may act as a resistance on the contrary and the driving efficiency may be lowered.
On the one hand, since the electric motorcar runs by electric power of a battery, it is important to avoid, as possible, an electric power consumption other than that required for running, and when a heating means for heating the lubrication oil is provided, how to obtain the electric power for operating the heating means becomes a problem.